Brake



July 25,1933. B, DICK 1,919,542

BRAKE Filed Dec. 2, 1927' v Inventor Patented July 25, 1933 a UNITEDSTATES PATENT OFFICE BURNS DICK, OF ST. LOUIS, MISSOURI, ASSIGN'OR TOWAGNER ELECTRIG CORPORATION,

OF ST. LOUIS, MISSOURI, CORPORATION OF BRAKE Application filed December2, 1927. Serial No. 237,165.

My invention relates to an improvement in brakes and is herein shown asembodied in a vehicle brake of the internal shoe type. The object of myinvention is to prevent, or at least postpone until after a long periodof use, the tendency of brakes to squeak and chatter. In brakes of theinternal shoe type herein described, and which embody brake shoespivoted at one end and provided with a lining engaging a surroundingbrake drum, the production of squeaks and chatters seems more likely tooccur when the pressure between the brake lining and drum near the freeend of the shoe exceeds the '1 pressure between the drum and the liningnear the heel or pivoted end of the shoe.

Brakes of the type referred to are commonly initially so adjusted thatthere is a smaller clearance, in off position of the brake shoe, betweenthedrum and lining at the heel of the shoe than between the drum and thelining at, the toe of the shoe. This adjustment causes a heavierpressure to be applied at the heel of the lining than at the toe inapplication of the brake and prevents ways stop when the heel and toeclearances have become the same? but, apparently due to the flexibilityof the drum and the brake shoe and supporting members and the frictionalreaction between the drum'and toe of the shoe, excess pressure on theheel of the shoe may continue until the wear has gone to the poi'nttowhere the off position clearance between the heel of the shoe and thedrum is greater than the clearance at the toe of the shoe. The tendencyto produce squeaks and chatters seems to begin when the clearancesapproach equality and to be emphasized when the heel clearance exceedsthe toe clearance. One object of my invention is to provide means forpreventing,

or at least substantially reducing squeaks and chatters in the type ofbrake above described.

The invention will be explained by reference to the accompanying drawingin which Figure 1 is an elevational View of a twoshoe internal brake ofa type in which my invention can be usefully embodied; Figure 2represents the face View of a shoe with a form of lining constructionembodying my invention; and Figures 3 and 4 represent alternative formsof lining.

In Figure 1 the brake drum 1 cooperates with the brake linings carriedby the pivotally mounted brake shoes 2.

{as above explained, the preferred initial ad uStment of the relation ofthe shoes to the drum is such as to have the clearance between the drumand lining at] the heel of the shoe less than the clearance between thedrum and the lining at the toe portion in the off position of the shoe.One suitable initial adjustment is to have the first mentioned clearancefive-thousandths of an inch and the latter ten-thousandths of an inch ina brake having the relative dimensions shown in Figure 1. Inaccordancewith my invention I'prevent the operation of the brakes from changingrelation of these clearances to a point where there is a tendency forthe toe of the lining to snub or seize the brake drum and thus producesqueaks and chatters, by so constructing the lining as to give itsusceptibility to more rapid wear at the toe than at the heel. This endmay be accom lished in a number of ways. 11 Figure 2 have shown thelining made up of two sections, 3 and 4, section 3 on the toe portion ofthe shoe having more rapid wearing characteristics than the section 4 atthe heelof the shoe, the wearing characteristics of the lining being ofcourse determinable by methods or materials of manufacture. A similarresult may be obtained by. the use of a liningof uniform characteristicsthroughout but reduced in a single piece of material if, by an suitablemeans, the heel portion of the lining be made harder or otherwise soconstructed or treated as to have greater wear resisting characteristicsthan the'toe portion. I prefer that the frictional coeflicients of. thetoe portions of linings used be the same as the remaining portion inorder that total braking-effect may not be materially reduced inrelation to shoe dimensions.

It will be understood that in the references'to off position clearancesherein I have assumed relations of pivots, centers and actuatinvmeansshown in Figure 1. Change of these positions would change 'actualclearance differences and as to any particular construction the adjustedactual clearances are preferably to be such thatin brake application theheel of the lining contacts with the drum-before the toe of the.

lining comes into contact. This relation is referred to 1n the clalmsasa dliference 1nv effective clearance between the drum and calconditions of pressure, drum surface and the like, rather than to therelative amount of wear actually occurring in the respective parts underuse in a brake.

It will be clear that when brake linings are formed in accordance withmy invention the susceptibility to more rapidwearing of the lining'atthe toe than at the heel will prevent, or at least delay for a longtime, such change in effective clearance as will result in lowerpressures between the heel of the lining and the drum than between thetoe of the lining and the drum and thus prevent the seizing action ofthe toe on the drum which results in squeaks and chatters. It will beunderstood that I do not bind or limit myself to any theory or b anystatement herein of causes of squeaking in brakes. I have definitelyascertained that with the arrangement herein described, em-

ploying a lining substantially as shown in Figure 4, the object of myinvention is accomplished and variations in the clearance adjustmentsand other features herein described as preferred may also producesatisfactory results. I therefore do not intend that the scope of myinvention be limited except as defined by thev appended claims.

Having fully described my invention, what I claim as new and desire tosecure by Letters Patent of the United States is:

1. In braking apparatus, a brake shoe pivoted at one end and having anarcuate surface, and a brake lining secured to said surface, the part ofthe lining nearest the pivoted end of the shoe having less susceptibilitto wear than the part furthest remove therefrom.

2. In braking apparatus, the combination with a brake drum, of a brakelining whose entire width is adapted to cooperate with the drum, saidlining having greater susceptibility to wear at one end of its effectivebraking surface than at the other end.

' o. In braking apparatus, the combination with a brake drum, of a brakelining whose entire width is adapted to cooperate with the drum, saidlining having substantially uniform frictional coeflicient throughoutits braking surface but having greater susceptibility to wear on onepart of said surface than on the other.

4. In braking apparatus, the combination with a brake drum, of a brakelining whose entire width is adapted to cooperate with the drum, saidlining having less braking surface per unit of length at one part thanat another.

5. In braking apparatus, the combination with a brake drum, of a brakelining whose entire width is adapted to cooperate with the drum, saidlining being of uniformmaterial throughout but having one end of itsbraking surface narrower than the other end.

6. In braking apparatus, the combination with a brake drum, of a brakelining whose entire width is adapted to cooperate with the drum, saidlining comprising two sections in end to end relation, one of which hasa other.

7. A brake shoe for vehicle wheel brakes comprising a body having abrake lining supporting surface, and means for pressing said liningagainst a cooperating brake member with a force per unit of length ofsaid brake lining varying substantially in accordance with the area ofsaid brake lining per unit of len th.

8. In a vehicle eel brake having an annular brake drum, brake lining forengagement' with-the drum, said lining increasing in effective widthfrom one end toward theother, and means for pressing said lining againstsaid brake drum, said means exerting a force on said lining varying fromend.

to end thereof substantlalilfy in proportion to the variation in the eective wldth of said lining.

9. In a vehicle wheel brake having a brake drum, a brake shoe comprisingan arcuate body member provided with a brake lining.

supporting surface and brake linin fixed to said surface for engagementwlth the brake drum, said lining increasing in efiecgreatersusceptibility to wear vthan the tive width from one end thereof towardthe other, and meansfor exerting a force on said lining varying from endto end thereof substantially in proportion to the variation in 5 theeffective width of said lining.

10. In a vehicle wheel brake having a brake drum, a brake shoe body fordisposition within the brake drum comprising a body having a surfacesubstantially concentrio with one wall of the drum, and a brake liningsecured to the body for engagement with the drum, said lining increasingin effective width from one end thereof toward the other, and means forpressing said lining against said drum by exerting a greater force onone end of said lining than on the other end of said lining.

11. In a vehicle wheel brake having a brake drum, a brake shoecomprising a body 2 member and a brake lining carried by the body memberfor engagement with the drum when the body is moved, said lining beinggreater in effective width at one end than at the other, and means forpressing said 5 lining against said drum by exerting a greater force onthe wider end of said lining than on the narrower end of said lining.

12. In a vehicle wheel brake having a brake drum, a brake shoecomprising a body 2 member and a brake lining carried by the body memberfor engagement with the drum when the body is moved, said lining beinggreater in surface area per unit of length at the heel than at the toeportion thereof, 5 and means for pressing said lining against said drumby exerting a greater force on the heel of said .lining than on the toeportion thereof.

13. A brake shoe for internally expanding vehicle wheel brakescomprising a rigid arcuate body, means for pivotally mounting the bodyat one end thereof, a brake lining supported upon the body and extendingsubstantially throughout the length thereof, said brake lining beingsubstantially greater in surface area per unit of length at that portionof the body nearer the pivotally mounted end than at the free end.

14. In a vehicle wheel brake having a brake drum, a brake lining forengagement with the drum, said lining increasing in effective width fromone end toward the other in a degree determinable by circumferentiallength of the lining, and means for pressing said lining against saiddrum with a force substantially proportional at all points along thelength of said lining to the efiective width of said lining at saidpoints.

' 15. A brake lining having agreater susceptibility to wear on onepartofits efiective braking surface than on another, and means for forcingparts .of said lining against a brake member inversely proportional tothe susceptibility to wear of said parts.

16. A brake lining having substantiallyc uniform frictional coefficientthroughout its braking surface but having greater susceptibility to wearon one part of said surface than on another, and means for exertingdifferent degrees of force on difierent parts ofsaid lining.

17. A brake lining having less braking surface per unit of length at onepart than at another, and means for applying force to said lining, saidforce varying per unit of length substantially in accordance with thecorresponding braking surface provided by said lining.

18. A brake shoe lining of uniform material throughout but having thetoe portion of its braking surface narrower than the heel portion, andmeans for applying greater force to sa id.heel portion than said toeportion.

19. A brake member providing a braking surface having a dimension oflength and a dimension of width,means for pressing the braking surfaceagainst a cooperating brake member with a force varying in amount alongone of said dimensions, the other dimension of. said braking surfacevarying in effective extent substantially proportionally to thevariation in said force to maintain a substantially equal unit pressureover the entire braking surface.

20. A brake member providing a braking surface having length and width,means for pressing the braking surface against a cooperating brakemember with a force varying in amount along the length of said surface,said surface varying in efi'ective portions of said shoe and africtional working surface of minimum area at the free portions of saidshoe.

23. In a brake apparatus, a rotatable member, and means normally bearingagainst said'rotatable member with difierent force amplitudes at spacedlocations during actuation of said apparatus and including a brakelining element 'having a frictional working surface of maximum area atthe.location of maximum force amplitude and a frictional workin at thelocation 0 plitude.

the minimum force amsurface of minimum area 24. In a brake apparatus, arotatable member, and means normally bearing against said rotatablemember with different force amplitudes at spaced locations duringactuation of said apparatus andincluding a brake lining element havin afixed base portion and a protrudin frictional working surface of varyingwidt ,the maximum width of said surface being located at the region ofmaximum force and the minimum width of said surface being located at theregion of minimum force.

25. In a brake apparatus, a rotatable member, and means normally bearingagainst said rotatable member with different force amplitudes at spacedlocations during actuation of said apparatus and including a brakelining element having a frictional said apparatus and including a brakelining -27. In brake apparatus, a brake drum, a

brake shoe, means normally urging successive portions of said brake shoetoward said drum with different force amplitudes at spaced locationsduring operation of said apparatus, and a brake lining on said brakeshoe, the area of successive portions .of the frictional surface of saidlinin being substantially proportional to the Iorce amplitudes at thecorresponding portions of said brake shoe.

28. In brake apparatus,a brake drum, a self energizing brake bandnormally urged toward said drum with different force amplitudes atspaced locations during operation of said apparatus, and a brake liningon said band, the area of successive portions of the frictional surface'of said lining being substantially proportional to the force amplitudesat the corresponding portions of said brake band. a

' BURNS DICK.

